Method of decolorizing blue jeans based on client-desired design

ABSTRACT

The present invention provides a method of decolorizing blue jeans based on a client-desired design. Hydrochloric acid (HOCl) and sodium chloride solution are provided to an electrolytic tub, and are electrolyzed to generate chlorine gas and hydrogen gas. Hypochlorous acid solution is separated from sodium hydroxide. Tapes are attached to the blue jeans to make a constant form. The tape-attached blue jeans are submerged in the hypochlorous acid to change a colorant of the blue jeans.

RELATED APPLICATION

[0001] This application relies for priority upon Korean PatentApplication No. 2001-13372, filed on Mar. 15, 2001, the contents ofwhich are herein incorporated by reference in their entirety.

DESCRIPTION

[0002] The present invention is a method of decolorizing blue jeans and,more particularly, to a method of decolorizing blue jeans based on theclient-desired design.

BACKGROUND OF THE INVENTION

[0003] Blue jeans are trousers that are made of fabrics obtained bycolorizing closely woven fabric with blue colorant such as indigo bluedye. Therefore, the blue jeans become favorite jeans due to toughness,durability, and practicality. Like other fashion clothes, blue jeanshave kept pace with various tastes or liking of users by changing theirforms and colors.

[0004] Since blue jeans are originally rough as well as tough, a user,maker or merchant often intentionally makes the blue jeans worn out by asandblasting or stonewashing process. The colors of initially colorizedblue jeans are generally dark, so that there may be a need for partialdecolorization thereof by reacting with a decolorant such as sodiumhypochlorite (HOCl) during a drum processing. Furthermore, by attachingtapes to parts of the blue jeans during decolorization thereof, theparts are not decolorized to attain desired patterns or shapes.

[0005] However, conventional methods of making patterns on the bluejeans have difficulty in attaining desired patterns and clear colors. Ina conventional decolorization process, a chemical solution such assodium hypochlorite or calcium hypochlorite is put into an amount ofwater having a temperature between 60° C. and 80° C. (if necessary,abrading materials are added). Together with the water containing thechemical solution, blue jeans are rotated in a drum for 30 minutes orlonger. In a case where tapes are attached to the blue jeans in order toattain a desired pattern, the water or other chemical materials may havean influence on the tapes. In addition, a high processing temperaturemay soften an adhesive element and turbulence may cause the tapes tothrust out from their original positions. Therefore, it is hard toattain the desired pattern. Further, if the tapes are thrust out fromthe blue jeans during the decolorization, tape-attached parts are alsodecolorized to make it hard to attain a clear color and pattern.

[0006] Also, the conventional decolorization method demands high costsfor raising the temperature of a processing solution and continuouslyproviding sodium hypochlorite and an amount of water. Wastewater isinevitably produced in the conventional decolorization. When thewastewater is discharged to a river, environmental pollution results.Therefore, if the wastewater is treated and discharged, additionallycosts are incurred.

SUMMARY OF THE INVENTION

[0007] A main purpose of the present invention is to provide a method ofdecolorizing blue jeans with a clear color and a desired design.

[0008] Another purpose of the present invention is to provide anenvironment-friendly method of decolorizing blue jeans, which is capableof preventing waste, pollution, and waste treating cost.

[0009] Still another purpose of the present invention is to provide amethod of decolorizing blue jeans, which is capable of cutting downdecolorization cost by retrieving a chemical material to be used as atreatment material in waste produced during decolorization.

[0010] One aspect of the present invention is a method of decolorizingblue jeans using the steps of ;providing hydrochloric acid and sodiumchloride solution to an electrolytic tub to generate chlorine gas andhydrogen gas, separating hypochlorous acid (HOCl) solution from sodiumhydroxide, attaching tapes to the blue jeans to make a constant form,and submerging the tape-attached blue jeans in the hypochlorous acid tochange the color of the blue jeans.

[0011] Another aspect of the present invention consists of providinghydrochloric acid (HOCl) and sodium chloride solution to an electrolytictub to generate chlorine gas and hydrogen gas, separating hypochlorousacid solution from sodium hydroxide, colorizing the blue jeans with anoil-based colorant oxidized by the hypochlorous acid to make a constantform, and submerging the tape-attached blue jeans in the hypochlorousacid to change the color of the blue jeans.

[0012] The oil-based colorant is identical to a colorant colorized onthe blue jeans. When additionally colorizing the blue jeans,colorization amount is controlled at each part of the blue jeans througha plurality of control steps.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a concept diagram showing the general structure of oneexample of an apparatus for decolorizing blue jeans according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] Although specific terms are used in the following description forthe sake of clarity, these terms are intended to refer only to theparticular feature of the invention selected for illustration and arenot intended to define or limit the scope of the invention.

[0015] Referring now to FIG. 1, an apparatus for decolorizing blue jeansincludes an electrolytic tub 10. A semipermeable membrane 7 is placed inthe center of the electrolytic tub 10. In the early stage, a smallamount of hydrochloric (HCl) solution and sodium chloride (NaCl)solution are provided to the electrolytic tub 10. Preferably, NaCl is0.1-7% solution by weight.

[0016] The electrolytic tub 10 has a cathode 5 and an anode 3.Generally, the cathode 5 is made of one selected from the groupconsisting of platinum, platinum-plated conductor, a material of highelectric conductivity that is not eroded by sodium hydroxide, and theanode 3 is made of stainless steel that is strong for the erosion. If avoltage is applied to the cathode 5 and the anode 3 by supplying a powerthereto, sodium ions dissociated from sodium chloride are induced to thecathode 5. As a result, an electron is gained to generate sodium metal.

[0017] The sodium metal immediately reacts with water to produce sodiumhydroxide. The sodium hydroxide is dissolved in the water to producesodium hydroxide solution. At this time, hydrogen gas is produced andexhausted. Chlorine ions are induced to the anode 3, so that an electronis lost to produce a chlorine molecule. A part of the chlorine moleculeis gasified to be exhausted into the air, and another part reacts withthe water to produce hydrogen chloride and hypochlorous acid. Thehydrogen chloride and the hypochlorous acid are immediately dissolved inthe water to produce hydrochloride solution and hypochlorous solution.The hypochlorous acid (HOCl) is an oxidant having a strong oxidizingpower. The oxidizing power of the hypochlorous acid (HOCl) is 40-80times stronger than that of sodium chlorate (NaOCl) which is an elementof a commercial sterilizing-bleaching agent. Although the membrane 7isolates a cathode space 8 from an anode space 9, sodium ions, chlorineions, and hydrogen ions are permeated well.

[0018] Therefore, the content of sodium chloride in the electrolytic tub10 is reduced as time passes. Further, the electrolytic tub 10 has thehydrochloride and hypochlorous solutions that are intensivelyconcentrated on the anode and cathode spaces 9 and 8. Since hydrochloricacid is induced to each of the cathode 5 and anode 3 to produce a partof chlorine and hydrogen, it is not intensively concentrated thereon.Generating materials of each of the cathode 5 and anode 3 arerepresented by chemical formulas 1 and 2 below.

Cl₂+H₂O=HCl+HOCl  [Chemical Formula 1]

2Na+2H₂O=2NaOH+H₂  [Chemical Formula 2]

[0019] The electrolytic tub 10 is connected, via a processing pipe, to aprocessing tub 30 in which a process for decolorizing blue jeans iscarried out. The processing pipe has an output pipe making a materialflow from the processing tub 30 to the electrolytic tub 10, and an inputpipe 18 making a material flow from the electrolytic tub 10 to theprocessing tub 30. A pump and valves for making solution flow areinstalled at the input pipe 18 and the output pipe. In this case, theinput pipe 18 may also serve as the output pipe (i.e., one pipe mayserve as input and output pipes) and the pump enables the solution tobi-directionally flow.

[0020] If a concentration of the hypochlorous acid reaches apredetermined level in the anode space 9 of the electrolytic tub 10,solution in the anode space 9 flows to the processing tub 30 via theinput pipe 18.

[0021] A chlorine trap duct 14 and a hydrogen trap duct 12 are installedat the electrolytic tub 10. The chlorine trap duct 14 traps chlorineproduced over the anode space 9, and the hydrogen trap duct 14 trapshydrogen produced over the anode space 8. Also, the ducts 12 and 14 areconnected to a scrubber 20 for processing a gas via a duct pipe 16 forcarrying the gas. On the duct pipe 16, a fan FAN may be installed forhelping to carry a gas and easily trapping the gas. A confluence may beformed in a center of the duct pipe 16 to mix trapped gases with oneanother.

[0022] Alternatively, the confluence may serve as a reaction chamberjust before scrubbing the trapped gases. In the confluence, hydrogenreacts with chlorine to produce a hydrogen chloride gas that is providedto a processing chamber in the scrubber 20.

[0023] A shower facility 22 is installed entirely over the processingchamber in the scrubber 20. A shower pipe 26, which is connected to thecathode 8 of the electrolytic tub 10, is connected to the showerfacility 22. A pump and a valve are mounted on the shower pipe 26 tocarry a chemical solution (here, sodium hydroxide filling most part ofthe cathode 8) to the processing chamber in the scrubber 20. In theprocessing chamber, the sodium hydroxide solution is sprayed through theshower facility 22. Most of the sprayed sodium hydroxide solution reactswith the hydrogen chloride provided to the processing chamber to producea sodium chloride solution. Most of the sodium chloride solutiondirectly drops to a retrieving tub incorporated with the processingchamber. Scattered minute solution drops are condensed and trapped by ade-mister installed at an upper part of the scrubber 20, and then flowsinto the retrieving tub.

[0024] Thus, contaminants are not discharged to the air while onlyinnoxious gases are exhausted via the scrubber 20. In the confluence ofthe duct pipe 16 and the scrubber 20, a chemical reaction is representedby chemical formulas 3 and 4 below.

H₂+Cl₂=2HCl  [Chemical Formula 3]

HCl+NaOH=NaCl+H₂O  [Chemical Formula 4]

[0025] A sodium chloride solution is put into a retrieving tub 24 thatis located at a lower part of the scrubber 20. The retrieving tub 24 isconnected to the electrolytic tub 10 via a retrieving pipe 32 having avalve and a pump. Thus, the sodium chloride solution, which is generatedin the scrubber 20 via the retrieving pipe 32, is carried to theelectrolytic tub 10. Since elements of the sodium chloride solution areall originated from the electrolytic tub 10, processing elements are tobe retrieved.

[0026] Decolorization-desired blue jeans 31 are submerged, for apredetermined time, in the processing tub 30 with the hypochlorous acid(partially containing hydrochloric acid or other materials) carried fromthe cathode and anode spaces 8 and 9. Since tapes protect partialsurfaces of the blue jeans 31, a chemical reaction is suppressed attape-attached parts. On the other hand, in unprotected parts, colorantelements for making a color of the blue jeans 31 react with thehypochlorous acid. This results in considerable oxidation of theunprotected parts. Further, a chlorination reaction may occur partially.Owing to the strong oxidizing power of the hypochlorous acid, thereaction is made at a temperature between 10° C. and 30° C., preferablybetween 18° C. and 26° C. While it is appreciated that the submergingtime is variable with the processing conditions, two to ten minutes aresufficient. Preferably, the tapes do not damage clothes of the bluejeans although they are removed after the decolorization process, andare treated by an adhesive agent which does not weaken an adhesive powerin spite of reaction with water or other decolorization chemicals.

[0027] With variation of the colorant elements, the blue jeans aregradually decolorized. A degree of the decolorization is controllablewith the submerging time, a concentration of the hypochlorous acid, aprocessing temperature. Since the hypochlorous acid used to decolorizethe blue jeans 31 are changed to hydrogen chloride, the hypochlorousacid solution in the processing tub 30 is changed to a solution mainlycontaining a diluted hydrochloric acid when the decolorization processis performed therein.

[0028] The diluted hydrochloric acid solution is provided to theelectrolytic tub 10 via the output pipe of the processing pipe. Thediluted hydrochloric acid solution is also made up of materials providedfrom the electrolytic tub 10. Therefore, a process for providing thediluted hydrochloric acid solution may be called a retrieving process. Achemical reaction in the processing tub 30 is represented by chemicalformulas 5 and 5 below.

R—H+HOCl=R—OH+HCl  [Chemical Formula 5]

R—H+HOCl=R—Cl+H₂O  [Chemical Formula 6]

[0029] wherein the R group (R—) is an atomic group having any structure,and a conventional colorant element is made up of an organic group.

[0030] Generally, oxidized or chlorinated colorant elements arecontinuously attached to the blue jeans. For that reason, the oxidizedor chlorinated colorant elements are not diffused to the processing tub30 and the diluted hydrochloric acid can be retrieved. If the changedcolorant elements are separated from the blue jeans to contaminate theprocessing tub 30, they must be eliminated by performing an extratreatment process.

[0031] Although it has been described that all the steps are separatelyperformed in this embodiment, a continuous process may be made in whicheach pipe continuously puts a material out by controlling a rotationspeed based on a content of provided materials and an apparatus andenvironmental conditions such as temperature and pressure for eachprocessing reaction. Since the continuous process does not requiremanpower for operating a valve or pump of each pipe, automation andmechanization can easily be realized in the whole process.

[0032] According to the present invention, because hypochlorous acidhaving a strong oxidizing power is used, it is not necessary to raise aprocessing temperature. Therefore, tapes are not separated from the bluejeans during a process for decolorizing the blue jeans to obtain adesign of client-desired form and clearness. Further, all materials arecirculated except oxygen or chlorine. If water for supplementing oxygenand a part of exhausted gas or a chlorine gas is supplemented, theprocess for decolorizing blue jeans can continuously be performed onlyby supplying electricity. Compared with a conventional process in whichall decolorizing elements are provided anew for one time treatment andwaste is inevitably created, the decolorizing process according to theinvention can be recycled only by supplying electricity andsupplementing eliminated elements. Thus, costs for providing materialand treating waste can be saved. First of all, the present inventionmakes it possible to realize an environment-friendly process.

What is claimed is:
 1. A method of decolorizing blue jeans, comprisingthe steps of: (a) providing and electrolyzing hydrochloric acid (HOCl)and sodium chloride solution to an electrolytic tub to generate chlorinegas and hydrogen gas, and separating hypochlorous acid solution fromsodium hydroxide; (b) attaching tapes to the blue jeans to make aconstant form; and (c) submerging the tape-attached blue jeans in thehypochlorous acid to change a colorant of the blue jeans.
 2. The methodas recited in claim 1, further comprising a step of reacting hydrogenchloride gas with the sodium hydroxide solution to produce sodiumchloride solution, wherein the hydrogen chloride gas is generated bytrapping and reacting the chlorine and hydrogen gases with each other.3. The method as recited in claim 2, wherein in the step (c), thecolorant is oxidized and a reaction is made to change the hypochlorousacid to the hydrochloric acid.
 4. The method as recited in claim 3,wherein the changing the colorant is made in the electrolytic tub and aprocessing tub; and wherein the producing the sodium chloride solutionis made in the electrolytic tub and a scrubber, further comprising astep of recycling the hydrochloric acid in the processing tub and thesodium chloride solution in the scrubber to the electrolytic tub.
 5. Themethod as recited in claim 4, wherein the steps are simultaneouslyperformed and each of the steps is continuously performed.
 6. The methodas recited in claim 1, wherein the changing the colorant is made at atemperature between 10° C. and 30° C.
 7. The method as recited in claim1, wherein the sodium chloride solution provided to the electrolytic tubcontains sodium chloride of 0.1-7% by weight.
 8. The method as recitedin claim 1, before the step (c), further comprising a step ofadditionally colorizing the blue jeans with an oil-based colorantoxidized by the hypochlorous acid to make a constant form.
 9. A methodof decolorizing blue jeans, comprising the steps of: (a) providing andelectrolyzing hydrochloric acid (HOCl) and sodium chloride solution toan electrolytic tub to generate chlorine gas and hydrogen gas, andseparating hypochlorous acid solution from sodium hydroxide; (b)additionally colorizing the blue jeans with an oil-based colorantoxidized by the hypochlorous acid to make a constant form; and (c)submerging the tape-attached blue jeans in the hypochlorous acid tochange a colorant of the blue jeans.
 10. The method as recited in claim9, wherein the oil-based colorant is identical to a colorant colorizedon the blue jeans and in the step (b), colorization amount is controlledat each part of the blue jeans through a plurality of control steps.